2 * Copyright (C) 1991, 1992 Linus Torvalds
3 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics
4 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
6 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
8 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
12 * This handles all read/write requests to block devices
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/backing-dev.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/highmem.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/string.h>
23 #include <linux/init.h>
24 #include <linux/completion.h>
25 #include <linux/slab.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/task_io_accounting_ops.h>
29 #include <linux/fault-inject.h>
30 #include <linux/list_sort.h>
32 #define CREATE_TRACE_POINTS
33 #include <trace/events/block.h>
37 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
38 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
39 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
41 static int __make_request(struct request_queue *q, struct bio *bio);
44 * For the allocated request tables
46 static struct kmem_cache *request_cachep;
49 * For queue allocation
51 struct kmem_cache *blk_requestq_cachep;
54 * Controlling structure to kblockd
56 static struct workqueue_struct *kblockd_workqueue;
58 static void drive_stat_acct(struct request *rq, int new_io)
60 struct hd_struct *part;
61 int rw = rq_data_dir(rq);
64 if (!blk_do_io_stat(rq))
67 cpu = part_stat_lock();
71 part_stat_inc(cpu, part, merges[rw]);
73 part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
74 if (!hd_struct_try_get(part)) {
76 * The partition is already being removed,
77 * the request will be accounted on the disk only
79 * We take a reference on disk->part0 although that
80 * partition will never be deleted, so we can treat
81 * it as any other partition.
83 part = &rq->rq_disk->part0;
86 part_round_stats(cpu, part);
87 part_inc_in_flight(part, rw);
94 void blk_queue_congestion_threshold(struct request_queue *q)
98 nr = q->nr_requests - (q->nr_requests / 8) + 1;
99 if (nr > q->nr_requests)
101 q->nr_congestion_on = nr;
103 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
106 q->nr_congestion_off = nr;
110 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
113 * Locates the passed device's request queue and returns the address of its
116 * Will return NULL if the request queue cannot be located.
118 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
120 struct backing_dev_info *ret = NULL;
121 struct request_queue *q = bdev_get_queue(bdev);
124 ret = &q->backing_dev_info;
127 EXPORT_SYMBOL(blk_get_backing_dev_info);
129 void blk_rq_init(struct request_queue *q, struct request *rq)
131 memset(rq, 0, sizeof(*rq));
133 INIT_LIST_HEAD(&rq->queuelist);
134 INIT_LIST_HEAD(&rq->timeout_list);
137 rq->__sector = (sector_t) -1;
138 INIT_HLIST_NODE(&rq->hash);
139 RB_CLEAR_NODE(&rq->rb_node);
141 rq->cmd_len = BLK_MAX_CDB;
144 rq->start_time = jiffies;
145 set_start_time_ns(rq);
148 EXPORT_SYMBOL(blk_rq_init);
150 static void req_bio_endio(struct request *rq, struct bio *bio,
151 unsigned int nbytes, int error)
154 clear_bit(BIO_UPTODATE, &bio->bi_flags);
155 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
158 if (unlikely(nbytes > bio->bi_size)) {
159 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
160 __func__, nbytes, bio->bi_size);
161 nbytes = bio->bi_size;
164 if (unlikely(rq->cmd_flags & REQ_QUIET))
165 set_bit(BIO_QUIET, &bio->bi_flags);
167 bio->bi_size -= nbytes;
168 bio->bi_sector += (nbytes >> 9);
170 if (bio_integrity(bio))
171 bio_integrity_advance(bio, nbytes);
173 /* don't actually finish bio if it's part of flush sequence */
174 if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
175 bio_endio(bio, error);
178 void blk_dump_rq_flags(struct request *rq, char *msg)
182 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
183 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
186 printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
187 (unsigned long long)blk_rq_pos(rq),
188 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
189 printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
190 rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
192 if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
193 printk(KERN_INFO " cdb: ");
194 for (bit = 0; bit < BLK_MAX_CDB; bit++)
195 printk("%02x ", rq->cmd[bit]);
199 EXPORT_SYMBOL(blk_dump_rq_flags);
201 static void blk_delay_work(struct work_struct *work)
203 struct request_queue *q;
205 q = container_of(work, struct request_queue, delay_work.work);
206 spin_lock_irq(q->queue_lock);
208 spin_unlock_irq(q->queue_lock);
212 * blk_delay_queue - restart queueing after defined interval
213 * @q: The &struct request_queue in question
214 * @msecs: Delay in msecs
217 * Sometimes queueing needs to be postponed for a little while, to allow
218 * resources to come back. This function will make sure that queueing is
219 * restarted around the specified time.
221 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
223 queue_delayed_work(kblockd_workqueue, &q->delay_work,
224 msecs_to_jiffies(msecs));
226 EXPORT_SYMBOL(blk_delay_queue);
229 * blk_start_queue - restart a previously stopped queue
230 * @q: The &struct request_queue in question
233 * blk_start_queue() will clear the stop flag on the queue, and call
234 * the request_fn for the queue if it was in a stopped state when
235 * entered. Also see blk_stop_queue(). Queue lock must be held.
237 void blk_start_queue(struct request_queue *q)
239 WARN_ON(!irqs_disabled());
241 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
244 EXPORT_SYMBOL(blk_start_queue);
247 * blk_stop_queue - stop a queue
248 * @q: The &struct request_queue in question
251 * The Linux block layer assumes that a block driver will consume all
252 * entries on the request queue when the request_fn strategy is called.
253 * Often this will not happen, because of hardware limitations (queue
254 * depth settings). If a device driver gets a 'queue full' response,
255 * or if it simply chooses not to queue more I/O at one point, it can
256 * call this function to prevent the request_fn from being called until
257 * the driver has signalled it's ready to go again. This happens by calling
258 * blk_start_queue() to restart queue operations. Queue lock must be held.
260 void blk_stop_queue(struct request_queue *q)
262 __cancel_delayed_work(&q->delay_work);
263 queue_flag_set(QUEUE_FLAG_STOPPED, q);
265 EXPORT_SYMBOL(blk_stop_queue);
268 * blk_sync_queue - cancel any pending callbacks on a queue
272 * The block layer may perform asynchronous callback activity
273 * on a queue, such as calling the unplug function after a timeout.
274 * A block device may call blk_sync_queue to ensure that any
275 * such activity is cancelled, thus allowing it to release resources
276 * that the callbacks might use. The caller must already have made sure
277 * that its ->make_request_fn will not re-add plugging prior to calling
280 * This function does not cancel any asynchronous activity arising
281 * out of elevator or throttling code. That would require elevaotor_exit()
282 * and blk_throtl_exit() to be called with queue lock initialized.
285 void blk_sync_queue(struct request_queue *q)
287 del_timer_sync(&q->timeout);
288 cancel_delayed_work_sync(&q->delay_work);
290 EXPORT_SYMBOL(blk_sync_queue);
293 * __blk_run_queue - run a single device queue
294 * @q: The queue to run
297 * See @blk_run_queue. This variant must be called with the queue lock
298 * held and interrupts disabled.
300 void __blk_run_queue(struct request_queue *q)
302 if (unlikely(blk_queue_stopped(q)))
307 EXPORT_SYMBOL(__blk_run_queue);
310 * blk_run_queue_async - run a single device queue in workqueue context
311 * @q: The queue to run
314 * Tells kblockd to perform the equivalent of @blk_run_queue on behalf
317 void blk_run_queue_async(struct request_queue *q)
319 if (likely(!blk_queue_stopped(q))) {
320 __cancel_delayed_work(&q->delay_work);
321 queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
324 EXPORT_SYMBOL(blk_run_queue_async);
327 * blk_run_queue - run a single device queue
328 * @q: The queue to run
331 * Invoke request handling on this queue, if it has pending work to do.
332 * May be used to restart queueing when a request has completed.
334 void blk_run_queue(struct request_queue *q)
338 spin_lock_irqsave(q->queue_lock, flags);
340 spin_unlock_irqrestore(q->queue_lock, flags);
342 EXPORT_SYMBOL(blk_run_queue);
344 void blk_put_queue(struct request_queue *q)
346 kobject_put(&q->kobj);
348 EXPORT_SYMBOL(blk_put_queue);
351 * Note: If a driver supplied the queue lock, it is disconnected
352 * by this function. The actual state of the lock doesn't matter
353 * here as the request_queue isn't accessible after this point
354 * (QUEUE_FLAG_DEAD is set) and no other requests will be queued.
356 void blk_cleanup_queue(struct request_queue *q)
359 * We know we have process context here, so we can be a little
360 * cautious and ensure that pending block actions on this device
361 * are done before moving on. Going into this function, we should
362 * not have processes doing IO to this device.
366 del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
367 mutex_lock(&q->sysfs_lock);
368 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
369 mutex_unlock(&q->sysfs_lock);
371 if (q->queue_lock != &q->__queue_lock)
372 q->queue_lock = &q->__queue_lock;
376 EXPORT_SYMBOL(blk_cleanup_queue);
378 static int blk_init_free_list(struct request_queue *q)
380 struct request_list *rl = &q->rq;
382 if (unlikely(rl->rq_pool))
385 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
386 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
388 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
389 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
391 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
392 mempool_free_slab, request_cachep, q->node);
400 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
402 return blk_alloc_queue_node(gfp_mask, -1);
404 EXPORT_SYMBOL(blk_alloc_queue);
406 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
408 struct request_queue *q;
411 q = kmem_cache_alloc_node(blk_requestq_cachep,
412 gfp_mask | __GFP_ZERO, node_id);
416 q->backing_dev_info.ra_pages =
417 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
418 q->backing_dev_info.state = 0;
419 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
420 q->backing_dev_info.name = "block";
423 err = bdi_init(&q->backing_dev_info);
425 kmem_cache_free(blk_requestq_cachep, q);
429 if (blk_throtl_init(q)) {
430 kmem_cache_free(blk_requestq_cachep, q);
434 setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
435 laptop_mode_timer_fn, (unsigned long) q);
436 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
437 INIT_LIST_HEAD(&q->timeout_list);
438 INIT_LIST_HEAD(&q->flush_queue[0]);
439 INIT_LIST_HEAD(&q->flush_queue[1]);
440 INIT_LIST_HEAD(&q->flush_data_in_flight);
441 INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
443 kobject_init(&q->kobj, &blk_queue_ktype);
445 mutex_init(&q->sysfs_lock);
446 spin_lock_init(&q->__queue_lock);
449 * By default initialize queue_lock to internal lock and driver can
450 * override it later if need be.
452 q->queue_lock = &q->__queue_lock;
456 EXPORT_SYMBOL(blk_alloc_queue_node);
459 * blk_init_queue - prepare a request queue for use with a block device
460 * @rfn: The function to be called to process requests that have been
461 * placed on the queue.
462 * @lock: Request queue spin lock
465 * If a block device wishes to use the standard request handling procedures,
466 * which sorts requests and coalesces adjacent requests, then it must
467 * call blk_init_queue(). The function @rfn will be called when there
468 * are requests on the queue that need to be processed. If the device
469 * supports plugging, then @rfn may not be called immediately when requests
470 * are available on the queue, but may be called at some time later instead.
471 * Plugged queues are generally unplugged when a buffer belonging to one
472 * of the requests on the queue is needed, or due to memory pressure.
474 * @rfn is not required, or even expected, to remove all requests off the
475 * queue, but only as many as it can handle at a time. If it does leave
476 * requests on the queue, it is responsible for arranging that the requests
477 * get dealt with eventually.
479 * The queue spin lock must be held while manipulating the requests on the
480 * request queue; this lock will be taken also from interrupt context, so irq
481 * disabling is needed for it.
483 * Function returns a pointer to the initialized request queue, or %NULL if
487 * blk_init_queue() must be paired with a blk_cleanup_queue() call
488 * when the block device is deactivated (such as at module unload).
491 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
493 return blk_init_queue_node(rfn, lock, -1);
495 EXPORT_SYMBOL(blk_init_queue);
497 struct request_queue *
498 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
500 struct request_queue *uninit_q, *q;
502 uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
506 q = blk_init_allocated_queue(uninit_q, rfn, lock);
508 blk_cleanup_queue(uninit_q);
512 EXPORT_SYMBOL(blk_init_queue_node);
514 struct request_queue *
515 blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
521 if (blk_init_free_list(q))
525 q->prep_rq_fn = NULL;
526 q->unprep_rq_fn = NULL;
527 q->queue_flags = QUEUE_FLAG_DEFAULT;
529 /* Override internal queue lock with supplied lock pointer */
531 q->queue_lock = lock;
534 * This also sets hw/phys segments, boundary and size
536 blk_queue_make_request(q, __make_request);
538 q->sg_reserved_size = INT_MAX;
543 if (!elevator_init(q, NULL)) {
544 blk_queue_congestion_threshold(q);
550 EXPORT_SYMBOL(blk_init_allocated_queue);
552 int blk_get_queue(struct request_queue *q)
554 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
555 kobject_get(&q->kobj);
561 EXPORT_SYMBOL(blk_get_queue);
563 static inline void blk_free_request(struct request_queue *q, struct request *rq)
565 if (rq->cmd_flags & REQ_ELVPRIV)
566 elv_put_request(q, rq);
567 mempool_free(rq, q->rq.rq_pool);
570 static struct request *
571 blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
573 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
580 rq->cmd_flags = flags | REQ_ALLOCED;
583 if (unlikely(elv_set_request(q, rq, gfp_mask))) {
584 mempool_free(rq, q->rq.rq_pool);
587 rq->cmd_flags |= REQ_ELVPRIV;
594 * ioc_batching returns true if the ioc is a valid batching request and
595 * should be given priority access to a request.
597 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
603 * Make sure the process is able to allocate at least 1 request
604 * even if the batch times out, otherwise we could theoretically
607 return ioc->nr_batch_requests == q->nr_batching ||
608 (ioc->nr_batch_requests > 0
609 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
613 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
614 * will cause the process to be a "batcher" on all queues in the system. This
615 * is the behaviour we want though - once it gets a wakeup it should be given
618 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
620 if (!ioc || ioc_batching(q, ioc))
623 ioc->nr_batch_requests = q->nr_batching;
624 ioc->last_waited = jiffies;
627 static void __freed_request(struct request_queue *q, int sync)
629 struct request_list *rl = &q->rq;
631 if (rl->count[sync] < queue_congestion_off_threshold(q))
632 blk_clear_queue_congested(q, sync);
634 if (rl->count[sync] + 1 <= q->nr_requests) {
635 if (waitqueue_active(&rl->wait[sync]))
636 wake_up(&rl->wait[sync]);
638 blk_clear_queue_full(q, sync);
643 * A request has just been released. Account for it, update the full and
644 * congestion status, wake up any waiters. Called under q->queue_lock.
646 static void freed_request(struct request_queue *q, int sync, int priv)
648 struct request_list *rl = &q->rq;
654 __freed_request(q, sync);
656 if (unlikely(rl->starved[sync ^ 1]))
657 __freed_request(q, sync ^ 1);
661 * Determine if elevator data should be initialized when allocating the
662 * request associated with @bio.
664 static bool blk_rq_should_init_elevator(struct bio *bio)
670 * Flush requests do not use the elevator so skip initialization.
671 * This allows a request to share the flush and elevator data.
673 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
680 * get_request - get a free request
681 * @q: request_queue to allocate request from
682 * @rw_flags: RW and SYNC flags
683 * @bio: bio to allocate request for (can be %NULL)
684 * @gfp_mask: allocation mask
686 * Get a free request from @q. This function may fail under memory
687 * pressure or if @q is dead.
689 * Must be callled with @q->queue_lock held and,
690 * Returns %NULL on failure, with @q->queue_lock held.
691 * Returns !%NULL on success, with @q->queue_lock *not held*.
693 static struct request *get_request(struct request_queue *q, int rw_flags,
694 struct bio *bio, gfp_t gfp_mask)
696 struct request *rq = NULL;
697 struct request_list *rl = &q->rq;
698 struct io_context *ioc = NULL;
699 const bool is_sync = rw_is_sync(rw_flags) != 0;
700 int may_queue, priv = 0;
702 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
705 may_queue = elv_may_queue(q, rw_flags);
706 if (may_queue == ELV_MQUEUE_NO)
709 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
710 if (rl->count[is_sync]+1 >= q->nr_requests) {
711 ioc = current_io_context(GFP_ATOMIC, q->node);
713 * The queue will fill after this allocation, so set
714 * it as full, and mark this process as "batching".
715 * This process will be allowed to complete a batch of
716 * requests, others will be blocked.
718 if (!blk_queue_full(q, is_sync)) {
719 ioc_set_batching(q, ioc);
720 blk_set_queue_full(q, is_sync);
722 if (may_queue != ELV_MQUEUE_MUST
723 && !ioc_batching(q, ioc)) {
725 * The queue is full and the allocating
726 * process is not a "batcher", and not
727 * exempted by the IO scheduler
733 blk_set_queue_congested(q, is_sync);
737 * Only allow batching queuers to allocate up to 50% over the defined
738 * limit of requests, otherwise we could have thousands of requests
739 * allocated with any setting of ->nr_requests
741 if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
744 rl->count[is_sync]++;
745 rl->starved[is_sync] = 0;
747 if (blk_rq_should_init_elevator(bio)) {
748 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
753 if (blk_queue_io_stat(q))
754 rw_flags |= REQ_IO_STAT;
755 spin_unlock_irq(q->queue_lock);
757 rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
760 * Allocation failed presumably due to memory. Undo anything
761 * we might have messed up.
763 * Allocating task should really be put onto the front of the
764 * wait queue, but this is pretty rare.
766 spin_lock_irq(q->queue_lock);
767 freed_request(q, is_sync, priv);
770 * in the very unlikely event that allocation failed and no
771 * requests for this direction was pending, mark us starved
772 * so that freeing of a request in the other direction will
773 * notice us. another possible fix would be to split the
774 * rq mempool into READ and WRITE
777 if (unlikely(rl->count[is_sync] == 0))
778 rl->starved[is_sync] = 1;
784 * ioc may be NULL here, and ioc_batching will be false. That's
785 * OK, if the queue is under the request limit then requests need
786 * not count toward the nr_batch_requests limit. There will always
787 * be some limit enforced by BLK_BATCH_TIME.
789 if (ioc_batching(q, ioc))
790 ioc->nr_batch_requests--;
792 trace_block_getrq(q, bio, rw_flags & 1);
798 * get_request_wait - get a free request with retry
799 * @q: request_queue to allocate request from
800 * @rw_flags: RW and SYNC flags
801 * @bio: bio to allocate request for (can be %NULL)
803 * Get a free request from @q. This function keeps retrying under memory
804 * pressure and fails iff @q is dead.
806 * Must be callled with @q->queue_lock held and,
807 * Returns %NULL on failure, with @q->queue_lock held.
808 * Returns !%NULL on success, with @q->queue_lock *not held*.
810 static struct request *get_request_wait(struct request_queue *q, int rw_flags,
813 const bool is_sync = rw_is_sync(rw_flags) != 0;
816 rq = get_request(q, rw_flags, bio, GFP_NOIO);
819 struct io_context *ioc;
820 struct request_list *rl = &q->rq;
822 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
825 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
826 TASK_UNINTERRUPTIBLE);
828 trace_block_sleeprq(q, bio, rw_flags & 1);
830 spin_unlock_irq(q->queue_lock);
834 * After sleeping, we become a "batching" process and
835 * will be able to allocate at least one request, and
836 * up to a big batch of them for a small period time.
837 * See ioc_batching, ioc_set_batching
839 ioc = current_io_context(GFP_NOIO, q->node);
840 ioc_set_batching(q, ioc);
842 spin_lock_irq(q->queue_lock);
843 finish_wait(&rl->wait[is_sync], &wait);
845 rq = get_request(q, rw_flags, bio, GFP_NOIO);
851 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
855 BUG_ON(rw != READ && rw != WRITE);
857 spin_lock_irq(q->queue_lock);
858 if (gfp_mask & __GFP_WAIT)
859 rq = get_request_wait(q, rw, NULL);
861 rq = get_request(q, rw, NULL, gfp_mask);
863 spin_unlock_irq(q->queue_lock);
864 /* q->queue_lock is unlocked at this point */
868 EXPORT_SYMBOL(blk_get_request);
871 * blk_make_request - given a bio, allocate a corresponding struct request.
872 * @q: target request queue
873 * @bio: The bio describing the memory mappings that will be submitted for IO.
874 * It may be a chained-bio properly constructed by block/bio layer.
875 * @gfp_mask: gfp flags to be used for memory allocation
877 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
878 * type commands. Where the struct request needs to be farther initialized by
879 * the caller. It is passed a &struct bio, which describes the memory info of
882 * The caller of blk_make_request must make sure that bi_io_vec
883 * are set to describe the memory buffers. That bio_data_dir() will return
884 * the needed direction of the request. (And all bio's in the passed bio-chain
885 * are properly set accordingly)
887 * If called under none-sleepable conditions, mapped bio buffers must not
888 * need bouncing, by calling the appropriate masked or flagged allocator,
889 * suitable for the target device. Otherwise the call to blk_queue_bounce will
892 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
893 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
894 * anything but the first bio in the chain. Otherwise you risk waiting for IO
895 * completion of a bio that hasn't been submitted yet, thus resulting in a
896 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
897 * of bio_alloc(), as that avoids the mempool deadlock.
898 * If possible a big IO should be split into smaller parts when allocation
899 * fails. Partial allocation should not be an error, or you risk a live-lock.
901 struct request *blk_make_request(struct request_queue *q, struct bio *bio,
904 struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
907 return ERR_PTR(-ENOMEM);
910 struct bio *bounce_bio = bio;
913 blk_queue_bounce(q, &bounce_bio);
914 ret = blk_rq_append_bio(q, rq, bounce_bio);
923 EXPORT_SYMBOL(blk_make_request);
926 * blk_requeue_request - put a request back on queue
927 * @q: request queue where request should be inserted
928 * @rq: request to be inserted
931 * Drivers often keep queueing requests until the hardware cannot accept
932 * more, when that condition happens we need to put the request back
933 * on the queue. Must be called with queue lock held.
935 void blk_requeue_request(struct request_queue *q, struct request *rq)
937 blk_delete_timer(rq);
938 blk_clear_rq_complete(rq);
939 trace_block_rq_requeue(q, rq);
941 if (blk_rq_tagged(rq))
942 blk_queue_end_tag(q, rq);
944 BUG_ON(blk_queued_rq(rq));
946 elv_requeue_request(q, rq);
948 EXPORT_SYMBOL(blk_requeue_request);
950 static void add_acct_request(struct request_queue *q, struct request *rq,
953 drive_stat_acct(rq, 1);
954 __elv_add_request(q, rq, where);
958 * blk_insert_request - insert a special request into a request queue
959 * @q: request queue where request should be inserted
960 * @rq: request to be inserted
961 * @at_head: insert request at head or tail of queue
962 * @data: private data
965 * Many block devices need to execute commands asynchronously, so they don't
966 * block the whole kernel from preemption during request execution. This is
967 * accomplished normally by inserting aritficial requests tagged as
968 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
969 * be scheduled for actual execution by the request queue.
971 * We have the option of inserting the head or the tail of the queue.
972 * Typically we use the tail for new ioctls and so forth. We use the head
973 * of the queue for things like a QUEUE_FULL message from a device, or a
974 * host that is unable to accept a particular command.
976 void blk_insert_request(struct request_queue *q, struct request *rq,
977 int at_head, void *data)
979 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
983 * tell I/O scheduler that this isn't a regular read/write (ie it
984 * must not attempt merges on this) and that it acts as a soft
987 rq->cmd_type = REQ_TYPE_SPECIAL;
991 spin_lock_irqsave(q->queue_lock, flags);
994 * If command is tagged, release the tag
996 if (blk_rq_tagged(rq))
997 blk_queue_end_tag(q, rq);
999 add_acct_request(q, rq, where);
1001 spin_unlock_irqrestore(q->queue_lock, flags);
1003 EXPORT_SYMBOL(blk_insert_request);
1005 static void part_round_stats_single(int cpu, struct hd_struct *part,
1008 if (now == part->stamp)
1011 if (part_in_flight(part)) {
1012 __part_stat_add(cpu, part, time_in_queue,
1013 part_in_flight(part) * (now - part->stamp));
1014 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1020 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1021 * @cpu: cpu number for stats access
1022 * @part: target partition
1024 * The average IO queue length and utilisation statistics are maintained
1025 * by observing the current state of the queue length and the amount of
1026 * time it has been in this state for.
1028 * Normally, that accounting is done on IO completion, but that can result
1029 * in more than a second's worth of IO being accounted for within any one
1030 * second, leading to >100% utilisation. To deal with that, we call this
1031 * function to do a round-off before returning the results when reading
1032 * /proc/diskstats. This accounts immediately for all queue usage up to
1033 * the current jiffies and restarts the counters again.
1035 void part_round_stats(int cpu, struct hd_struct *part)
1037 unsigned long now = jiffies;
1040 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1041 part_round_stats_single(cpu, part, now);
1043 EXPORT_SYMBOL_GPL(part_round_stats);
1046 * queue lock must be held
1048 void __blk_put_request(struct request_queue *q, struct request *req)
1052 if (unlikely(--req->ref_count))
1055 elv_completed_request(q, req);
1057 /* this is a bio leak */
1058 WARN_ON(req->bio != NULL);
1061 * Request may not have originated from ll_rw_blk. if not,
1062 * it didn't come out of our reserved rq pools
1064 if (req->cmd_flags & REQ_ALLOCED) {
1065 int is_sync = rq_is_sync(req) != 0;
1066 int priv = req->cmd_flags & REQ_ELVPRIV;
1068 BUG_ON(!list_empty(&req->queuelist));
1069 BUG_ON(!hlist_unhashed(&req->hash));
1071 blk_free_request(q, req);
1072 freed_request(q, is_sync, priv);
1075 EXPORT_SYMBOL_GPL(__blk_put_request);
1077 void blk_put_request(struct request *req)
1079 unsigned long flags;
1080 struct request_queue *q = req->q;
1082 spin_lock_irqsave(q->queue_lock, flags);
1083 __blk_put_request(q, req);
1084 spin_unlock_irqrestore(q->queue_lock, flags);
1086 EXPORT_SYMBOL(blk_put_request);
1089 * blk_add_request_payload - add a payload to a request
1090 * @rq: request to update
1091 * @page: page backing the payload
1092 * @len: length of the payload.
1094 * This allows to later add a payload to an already submitted request by
1095 * a block driver. The driver needs to take care of freeing the payload
1098 * Note that this is a quite horrible hack and nothing but handling of
1099 * discard requests should ever use it.
1101 void blk_add_request_payload(struct request *rq, struct page *page,
1104 struct bio *bio = rq->bio;
1106 bio->bi_io_vec->bv_page = page;
1107 bio->bi_io_vec->bv_offset = 0;
1108 bio->bi_io_vec->bv_len = len;
1112 bio->bi_phys_segments = 1;
1114 rq->__data_len = rq->resid_len = len;
1115 rq->nr_phys_segments = 1;
1116 rq->buffer = bio_data(bio);
1118 EXPORT_SYMBOL_GPL(blk_add_request_payload);
1120 static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1123 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1125 if (!ll_back_merge_fn(q, req, bio))
1128 trace_block_bio_backmerge(q, bio);
1130 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1131 blk_rq_set_mixed_merge(req);
1133 req->biotail->bi_next = bio;
1135 req->__data_len += bio->bi_size;
1136 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1138 drive_stat_acct(req, 0);
1139 elv_bio_merged(q, req, bio);
1143 static bool bio_attempt_front_merge(struct request_queue *q,
1144 struct request *req, struct bio *bio)
1146 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1148 if (!ll_front_merge_fn(q, req, bio))
1151 trace_block_bio_frontmerge(q, bio);
1153 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1154 blk_rq_set_mixed_merge(req);
1156 bio->bi_next = req->bio;
1160 * may not be valid. if the low level driver said
1161 * it didn't need a bounce buffer then it better
1162 * not touch req->buffer either...
1164 req->buffer = bio_data(bio);
1165 req->__sector = bio->bi_sector;
1166 req->__data_len += bio->bi_size;
1167 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1169 drive_stat_acct(req, 0);
1170 elv_bio_merged(q, req, bio);
1175 * Attempts to merge with the plugged list in the current process. Returns
1176 * true if merge was successful, otherwise false.
1178 static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q,
1181 struct blk_plug *plug;
1189 list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1195 el_ret = elv_try_merge(rq, bio);
1196 if (el_ret == ELEVATOR_BACK_MERGE) {
1197 ret = bio_attempt_back_merge(q, rq, bio);
1200 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1201 ret = bio_attempt_front_merge(q, rq, bio);
1210 void init_request_from_bio(struct request *req, struct bio *bio)
1212 req->cpu = bio->bi_comp_cpu;
1213 req->cmd_type = REQ_TYPE_FS;
1215 req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1216 if (bio->bi_rw & REQ_RAHEAD)
1217 req->cmd_flags |= REQ_FAILFAST_MASK;
1220 req->__sector = bio->bi_sector;
1221 req->ioprio = bio_prio(bio);
1222 blk_rq_bio_prep(req->q, req, bio);
1225 static int __make_request(struct request_queue *q, struct bio *bio)
1227 const bool sync = !!(bio->bi_rw & REQ_SYNC);
1228 struct blk_plug *plug;
1229 int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1230 struct request *req;
1233 * low level driver can indicate that it wants pages above a
1234 * certain limit bounced to low memory (ie for highmem, or even
1235 * ISA dma in theory)
1237 blk_queue_bounce(q, &bio);
1239 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1240 spin_lock_irq(q->queue_lock);
1241 where = ELEVATOR_INSERT_FLUSH;
1246 * Check if we can merge with the plugged list before grabbing
1249 if (attempt_plug_merge(current, q, bio))
1252 spin_lock_irq(q->queue_lock);
1254 el_ret = elv_merge(q, &req, bio);
1255 if (el_ret == ELEVATOR_BACK_MERGE) {
1256 if (bio_attempt_back_merge(q, req, bio)) {
1257 if (!attempt_back_merge(q, req))
1258 elv_merged_request(q, req, el_ret);
1261 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1262 if (bio_attempt_front_merge(q, req, bio)) {
1263 if (!attempt_front_merge(q, req))
1264 elv_merged_request(q, req, el_ret);
1271 * This sync check and mask will be re-done in init_request_from_bio(),
1272 * but we need to set it earlier to expose the sync flag to the
1273 * rq allocator and io schedulers.
1275 rw_flags = bio_data_dir(bio);
1277 rw_flags |= REQ_SYNC;
1280 * Grab a free request. This is might sleep but can not fail.
1281 * Returns with the queue unlocked.
1283 req = get_request_wait(q, rw_flags, bio);
1284 if (unlikely(!req)) {
1285 bio_endio(bio, -ENODEV); /* @q is dead */
1290 * After dropping the lock and possibly sleeping here, our request
1291 * may now be mergeable after it had proven unmergeable (above).
1292 * We don't worry about that case for efficiency. It won't happen
1293 * often, and the elevators are able to handle it.
1295 init_request_from_bio(req, bio);
1297 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1298 bio_flagged(bio, BIO_CPU_AFFINE)) {
1299 req->cpu = blk_cpu_to_group(get_cpu());
1303 plug = current->plug;
1306 * If this is the first request added after a plug, fire
1307 * of a plug trace. If others have been added before, check
1308 * if we have multiple devices in this plug. If so, make a
1309 * note to sort the list before dispatch.
1311 if (list_empty(&plug->list))
1312 trace_block_plug(q);
1313 else if (!plug->should_sort) {
1314 struct request *__rq;
1316 __rq = list_entry_rq(plug->list.prev);
1318 plug->should_sort = 1;
1320 list_add_tail(&req->queuelist, &plug->list);
1321 drive_stat_acct(req, 1);
1323 spin_lock_irq(q->queue_lock);
1324 add_acct_request(q, req, where);
1327 spin_unlock_irq(q->queue_lock);
1334 * If bio->bi_dev is a partition, remap the location
1336 static inline void blk_partition_remap(struct bio *bio)
1338 struct block_device *bdev = bio->bi_bdev;
1340 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1341 struct hd_struct *p = bdev->bd_part;
1343 bio->bi_sector += p->start_sect;
1344 bio->bi_bdev = bdev->bd_contains;
1346 trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1348 bio->bi_sector - p->start_sect);
1352 static void handle_bad_sector(struct bio *bio)
1354 char b[BDEVNAME_SIZE];
1356 printk(KERN_INFO "attempt to access beyond end of device\n");
1357 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1358 bdevname(bio->bi_bdev, b),
1360 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1361 (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1363 set_bit(BIO_EOF, &bio->bi_flags);
1366 #ifdef CONFIG_FAIL_MAKE_REQUEST
1368 static DECLARE_FAULT_ATTR(fail_make_request);
1370 static int __init setup_fail_make_request(char *str)
1372 return setup_fault_attr(&fail_make_request, str);
1374 __setup("fail_make_request=", setup_fail_make_request);
1376 static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1378 return part->make_it_fail && should_fail(&fail_make_request, bytes);
1381 static int __init fail_make_request_debugfs(void)
1383 return init_fault_attr_dentries(&fail_make_request,
1384 "fail_make_request");
1387 late_initcall(fail_make_request_debugfs);
1389 #else /* CONFIG_FAIL_MAKE_REQUEST */
1391 static inline bool should_fail_request(struct hd_struct *part,
1397 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1400 * Check whether this bio extends beyond the end of the device.
1402 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1409 /* Test device or partition size, when known. */
1410 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1412 sector_t sector = bio->bi_sector;
1414 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1416 * This may well happen - the kernel calls bread()
1417 * without checking the size of the device, e.g., when
1418 * mounting a device.
1420 handle_bad_sector(bio);
1429 * generic_make_request - hand a buffer to its device driver for I/O
1430 * @bio: The bio describing the location in memory and on the device.
1432 * generic_make_request() is used to make I/O requests of block
1433 * devices. It is passed a &struct bio, which describes the I/O that needs
1436 * generic_make_request() does not return any status. The
1437 * success/failure status of the request, along with notification of
1438 * completion, is delivered asynchronously through the bio->bi_end_io
1439 * function described (one day) else where.
1441 * The caller of generic_make_request must make sure that bi_io_vec
1442 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1443 * set to describe the device address, and the
1444 * bi_end_io and optionally bi_private are set to describe how
1445 * completion notification should be signaled.
1447 * generic_make_request and the drivers it calls may use bi_next if this
1448 * bio happens to be merged with someone else, and may change bi_dev and
1449 * bi_sector for remaps as it sees fit. So the values of these fields
1450 * should NOT be depended on after the call to generic_make_request.
1452 static inline void __generic_make_request(struct bio *bio)
1454 struct request_queue *q;
1455 sector_t old_sector;
1456 int ret, nr_sectors = bio_sectors(bio);
1462 if (bio_check_eod(bio, nr_sectors))
1466 * Resolve the mapping until finished. (drivers are
1467 * still free to implement/resolve their own stacking
1468 * by explicitly returning 0)
1470 * NOTE: we don't repeat the blk_size check for each new device.
1471 * Stacking drivers are expected to know what they are doing.
1476 char b[BDEVNAME_SIZE];
1477 struct hd_struct *part;
1479 q = bdev_get_queue(bio->bi_bdev);
1482 "generic_make_request: Trying to access "
1483 "nonexistent block-device %s (%Lu)\n",
1484 bdevname(bio->bi_bdev, b),
1485 (long long) bio->bi_sector);
1489 if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1490 nr_sectors > queue_max_hw_sectors(q))) {
1491 printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1492 bdevname(bio->bi_bdev, b),
1494 queue_max_hw_sectors(q));
1498 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1501 part = bio->bi_bdev->bd_part;
1502 if (should_fail_request(part, bio->bi_size) ||
1503 should_fail_request(&part_to_disk(part)->part0,
1508 * If this device has partitions, remap block n
1509 * of partition p to block n+start(p) of the disk.
1511 blk_partition_remap(bio);
1513 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1516 if (old_sector != -1)
1517 trace_block_bio_remap(q, bio, old_dev, old_sector);
1519 old_sector = bio->bi_sector;
1520 old_dev = bio->bi_bdev->bd_dev;
1522 if (bio_check_eod(bio, nr_sectors))
1526 * Filter flush bio's early so that make_request based
1527 * drivers without flush support don't have to worry
1530 if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1531 bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1538 if ((bio->bi_rw & REQ_DISCARD) &&
1539 (!blk_queue_discard(q) ||
1540 ((bio->bi_rw & REQ_SECURE) &&
1541 !blk_queue_secdiscard(q)))) {
1546 if (blk_throtl_bio(q, &bio))
1550 * If bio = NULL, bio has been throttled and will be submitted
1556 trace_block_bio_queue(q, bio);
1558 ret = q->make_request_fn(q, bio);
1564 bio_endio(bio, err);
1568 * We only want one ->make_request_fn to be active at a time,
1569 * else stack usage with stacked devices could be a problem.
1570 * So use current->bio_list to keep a list of requests
1571 * submited by a make_request_fn function.
1572 * current->bio_list is also used as a flag to say if
1573 * generic_make_request is currently active in this task or not.
1574 * If it is NULL, then no make_request is active. If it is non-NULL,
1575 * then a make_request is active, and new requests should be added
1578 void generic_make_request(struct bio *bio)
1580 struct bio_list bio_list_on_stack;
1582 if (current->bio_list) {
1583 /* make_request is active */
1584 bio_list_add(current->bio_list, bio);
1587 /* following loop may be a bit non-obvious, and so deserves some
1589 * Before entering the loop, bio->bi_next is NULL (as all callers
1590 * ensure that) so we have a list with a single bio.
1591 * We pretend that we have just taken it off a longer list, so
1592 * we assign bio_list to a pointer to the bio_list_on_stack,
1593 * thus initialising the bio_list of new bios to be
1594 * added. __generic_make_request may indeed add some more bios
1595 * through a recursive call to generic_make_request. If it
1596 * did, we find a non-NULL value in bio_list and re-enter the loop
1597 * from the top. In this case we really did just take the bio
1598 * of the top of the list (no pretending) and so remove it from
1599 * bio_list, and call into __generic_make_request again.
1601 * The loop was structured like this to make only one call to
1602 * __generic_make_request (which is important as it is large and
1603 * inlined) and to keep the structure simple.
1605 BUG_ON(bio->bi_next);
1606 bio_list_init(&bio_list_on_stack);
1607 current->bio_list = &bio_list_on_stack;
1609 __generic_make_request(bio);
1610 bio = bio_list_pop(current->bio_list);
1612 current->bio_list = NULL; /* deactivate */
1614 EXPORT_SYMBOL(generic_make_request);
1617 * submit_bio - submit a bio to the block device layer for I/O
1618 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1619 * @bio: The &struct bio which describes the I/O
1621 * submit_bio() is very similar in purpose to generic_make_request(), and
1622 * uses that function to do most of the work. Both are fairly rough
1623 * interfaces; @bio must be presetup and ready for I/O.
1626 void submit_bio(int rw, struct bio *bio)
1628 int count = bio_sectors(bio);
1633 * If it's a regular read/write or a barrier with data attached,
1634 * go through the normal accounting stuff before submission.
1636 if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1638 count_vm_events(PGPGOUT, count);
1640 task_io_account_read(bio->bi_size);
1641 count_vm_events(PGPGIN, count);
1644 if (unlikely(block_dump)) {
1645 char b[BDEVNAME_SIZE];
1646 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1647 current->comm, task_pid_nr(current),
1648 (rw & WRITE) ? "WRITE" : "READ",
1649 (unsigned long long)bio->bi_sector,
1650 bdevname(bio->bi_bdev, b),
1655 generic_make_request(bio);
1657 EXPORT_SYMBOL(submit_bio);
1660 * blk_rq_check_limits - Helper function to check a request for the queue limit
1662 * @rq: the request being checked
1665 * @rq may have been made based on weaker limitations of upper-level queues
1666 * in request stacking drivers, and it may violate the limitation of @q.
1667 * Since the block layer and the underlying device driver trust @rq
1668 * after it is inserted to @q, it should be checked against @q before
1669 * the insertion using this generic function.
1671 * This function should also be useful for request stacking drivers
1672 * in some cases below, so export this function.
1673 * Request stacking drivers like request-based dm may change the queue
1674 * limits while requests are in the queue (e.g. dm's table swapping).
1675 * Such request stacking drivers should check those requests agaist
1676 * the new queue limits again when they dispatch those requests,
1677 * although such checkings are also done against the old queue limits
1678 * when submitting requests.
1680 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1682 if (rq->cmd_flags & REQ_DISCARD)
1685 if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1686 blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1687 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1692 * queue's settings related to segment counting like q->bounce_pfn
1693 * may differ from that of other stacking queues.
1694 * Recalculate it to check the request correctly on this queue's
1697 blk_recalc_rq_segments(rq);
1698 if (rq->nr_phys_segments > queue_max_segments(q)) {
1699 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1705 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1708 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1709 * @q: the queue to submit the request
1710 * @rq: the request being queued
1712 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1714 unsigned long flags;
1716 if (blk_rq_check_limits(q, rq))
1720 should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1723 spin_lock_irqsave(q->queue_lock, flags);
1726 * Submitting request must be dequeued before calling this function
1727 * because it will be linked to another request_queue
1729 BUG_ON(blk_queued_rq(rq));
1731 add_acct_request(q, rq, ELEVATOR_INSERT_BACK);
1732 spin_unlock_irqrestore(q->queue_lock, flags);
1736 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1739 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1740 * @rq: request to examine
1743 * A request could be merge of IOs which require different failure
1744 * handling. This function determines the number of bytes which
1745 * can be failed from the beginning of the request without
1746 * crossing into area which need to be retried further.
1749 * The number of bytes to fail.
1752 * queue_lock must be held.
1754 unsigned int blk_rq_err_bytes(const struct request *rq)
1756 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1757 unsigned int bytes = 0;
1760 if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1761 return blk_rq_bytes(rq);
1764 * Currently the only 'mixing' which can happen is between
1765 * different fastfail types. We can safely fail portions
1766 * which have all the failfast bits that the first one has -
1767 * the ones which are at least as eager to fail as the first
1770 for (bio = rq->bio; bio; bio = bio->bi_next) {
1771 if ((bio->bi_rw & ff) != ff)
1773 bytes += bio->bi_size;
1776 /* this could lead to infinite loop */
1777 BUG_ON(blk_rq_bytes(rq) && !bytes);
1780 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1782 static void blk_account_io_completion(struct request *req, unsigned int bytes)
1784 if (blk_do_io_stat(req)) {
1785 const int rw = rq_data_dir(req);
1786 struct hd_struct *part;
1789 cpu = part_stat_lock();
1791 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1796 static void blk_account_io_done(struct request *req)
1799 * Account IO completion. flush_rq isn't accounted as a
1800 * normal IO on queueing nor completion. Accounting the
1801 * containing request is enough.
1803 if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
1804 unsigned long duration = jiffies - req->start_time;
1805 const int rw = rq_data_dir(req);
1806 struct hd_struct *part;
1809 cpu = part_stat_lock();
1812 part_stat_inc(cpu, part, ios[rw]);
1813 part_stat_add(cpu, part, ticks[rw], duration);
1814 part_round_stats(cpu, part);
1815 part_dec_in_flight(part, rw);
1817 hd_struct_put(part);
1823 * blk_peek_request - peek at the top of a request queue
1824 * @q: request queue to peek at
1827 * Return the request at the top of @q. The returned request
1828 * should be started using blk_start_request() before LLD starts
1832 * Pointer to the request at the top of @q if available. Null
1836 * queue_lock must be held.
1838 struct request *blk_peek_request(struct request_queue *q)
1843 while ((rq = __elv_next_request(q)) != NULL) {
1844 if (!(rq->cmd_flags & REQ_STARTED)) {
1846 * This is the first time the device driver
1847 * sees this request (possibly after
1848 * requeueing). Notify IO scheduler.
1850 if (rq->cmd_flags & REQ_SORTED)
1851 elv_activate_rq(q, rq);
1854 * just mark as started even if we don't start
1855 * it, a request that has been delayed should
1856 * not be passed by new incoming requests
1858 rq->cmd_flags |= REQ_STARTED;
1859 trace_block_rq_issue(q, rq);
1862 if (!q->boundary_rq || q->boundary_rq == rq) {
1863 q->end_sector = rq_end_sector(rq);
1864 q->boundary_rq = NULL;
1867 if (rq->cmd_flags & REQ_DONTPREP)
1870 if (q->dma_drain_size && blk_rq_bytes(rq)) {
1872 * make sure space for the drain appears we
1873 * know we can do this because max_hw_segments
1874 * has been adjusted to be one fewer than the
1877 rq->nr_phys_segments++;
1883 ret = q->prep_rq_fn(q, rq);
1884 if (ret == BLKPREP_OK) {
1886 } else if (ret == BLKPREP_DEFER) {
1888 * the request may have been (partially) prepped.
1889 * we need to keep this request in the front to
1890 * avoid resource deadlock. REQ_STARTED will
1891 * prevent other fs requests from passing this one.
1893 if (q->dma_drain_size && blk_rq_bytes(rq) &&
1894 !(rq->cmd_flags & REQ_DONTPREP)) {
1896 * remove the space for the drain we added
1897 * so that we don't add it again
1899 --rq->nr_phys_segments;
1904 } else if (ret == BLKPREP_KILL) {
1905 rq->cmd_flags |= REQ_QUIET;
1907 * Mark this request as started so we don't trigger
1908 * any debug logic in the end I/O path.
1910 blk_start_request(rq);
1911 __blk_end_request_all(rq, -EIO);
1913 printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
1920 EXPORT_SYMBOL(blk_peek_request);
1922 void blk_dequeue_request(struct request *rq)
1924 struct request_queue *q = rq->q;
1926 BUG_ON(list_empty(&rq->queuelist));
1927 BUG_ON(ELV_ON_HASH(rq));
1929 list_del_init(&rq->queuelist);
1932 * the time frame between a request being removed from the lists
1933 * and to it is freed is accounted as io that is in progress at
1936 if (blk_account_rq(rq)) {
1937 q->in_flight[rq_is_sync(rq)]++;
1938 set_io_start_time_ns(rq);
1943 * blk_start_request - start request processing on the driver
1944 * @req: request to dequeue
1947 * Dequeue @req and start timeout timer on it. This hands off the
1948 * request to the driver.
1950 * Block internal functions which don't want to start timer should
1951 * call blk_dequeue_request().
1954 * queue_lock must be held.
1956 void blk_start_request(struct request *req)
1958 blk_dequeue_request(req);
1961 * We are now handing the request to the hardware, initialize
1962 * resid_len to full count and add the timeout handler.
1964 req->resid_len = blk_rq_bytes(req);
1965 if (unlikely(blk_bidi_rq(req)))
1966 req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
1970 EXPORT_SYMBOL(blk_start_request);
1973 * blk_fetch_request - fetch a request from a request queue
1974 * @q: request queue to fetch a request from
1977 * Return the request at the top of @q. The request is started on
1978 * return and LLD can start processing it immediately.
1981 * Pointer to the request at the top of @q if available. Null
1985 * queue_lock must be held.
1987 struct request *blk_fetch_request(struct request_queue *q)
1991 rq = blk_peek_request(q);
1993 blk_start_request(rq);
1996 EXPORT_SYMBOL(blk_fetch_request);
1999 * blk_update_request - Special helper function for request stacking drivers
2000 * @req: the request being processed
2001 * @error: %0 for success, < %0 for error
2002 * @nr_bytes: number of bytes to complete @req
2005 * Ends I/O on a number of bytes attached to @req, but doesn't complete
2006 * the request structure even if @req doesn't have leftover.
2007 * If @req has leftover, sets it up for the next range of segments.
2009 * This special helper function is only for request stacking drivers
2010 * (e.g. request-based dm) so that they can handle partial completion.
2011 * Actual device drivers should use blk_end_request instead.
2013 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2014 * %false return from this function.
2017 * %false - this request doesn't have any more data
2018 * %true - this request has more data
2020 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2022 int total_bytes, bio_nbytes, next_idx = 0;
2028 trace_block_rq_complete(req->q, req);
2031 * For fs requests, rq is just carrier of independent bio's
2032 * and each partial completion should be handled separately.
2033 * Reset per-request error on each partial completion.
2035 * TODO: tj: This is too subtle. It would be better to let
2036 * low level drivers do what they see fit.
2038 if (req->cmd_type == REQ_TYPE_FS)
2041 if (error && req->cmd_type == REQ_TYPE_FS &&
2042 !(req->cmd_flags & REQ_QUIET)) {
2047 error_type = "recoverable transport";
2050 error_type = "critical target";
2053 error_type = "critical nexus";
2060 printk(KERN_DEBUG "end_request: %s error, dev %s, sector %llu\n",
2061 error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2062 (unsigned long long)blk_rq_pos(req));
2065 blk_account_io_completion(req, nr_bytes);
2067 total_bytes = bio_nbytes = 0;
2068 while ((bio = req->bio) != NULL) {
2071 if (nr_bytes >= bio->bi_size) {
2072 req->bio = bio->bi_next;
2073 nbytes = bio->bi_size;
2074 req_bio_endio(req, bio, nbytes, error);
2078 int idx = bio->bi_idx + next_idx;
2080 if (unlikely(idx >= bio->bi_vcnt)) {
2081 blk_dump_rq_flags(req, "__end_that");
2082 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2083 __func__, idx, bio->bi_vcnt);
2087 nbytes = bio_iovec_idx(bio, idx)->bv_len;
2088 BIO_BUG_ON(nbytes > bio->bi_size);
2091 * not a complete bvec done
2093 if (unlikely(nbytes > nr_bytes)) {
2094 bio_nbytes += nr_bytes;
2095 total_bytes += nr_bytes;
2100 * advance to the next vector
2103 bio_nbytes += nbytes;
2106 total_bytes += nbytes;
2112 * end more in this run, or just return 'not-done'
2114 if (unlikely(nr_bytes <= 0))
2124 * Reset counters so that the request stacking driver
2125 * can find how many bytes remain in the request
2128 req->__data_len = 0;
2133 * if the request wasn't completed, update state
2136 req_bio_endio(req, bio, bio_nbytes, error);
2137 bio->bi_idx += next_idx;
2138 bio_iovec(bio)->bv_offset += nr_bytes;
2139 bio_iovec(bio)->bv_len -= nr_bytes;
2142 req->__data_len -= total_bytes;
2143 req->buffer = bio_data(req->bio);
2145 /* update sector only for requests with clear definition of sector */
2146 if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2147 req->__sector += total_bytes >> 9;
2149 /* mixed attributes always follow the first bio */
2150 if (req->cmd_flags & REQ_MIXED_MERGE) {
2151 req->cmd_flags &= ~REQ_FAILFAST_MASK;
2152 req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2156 * If total number of sectors is less than the first segment
2157 * size, something has gone terribly wrong.
2159 if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2160 blk_dump_rq_flags(req, "request botched");
2161 req->__data_len = blk_rq_cur_bytes(req);
2164 /* recalculate the number of segments */
2165 blk_recalc_rq_segments(req);
2169 EXPORT_SYMBOL_GPL(blk_update_request);
2171 static bool blk_update_bidi_request(struct request *rq, int error,
2172 unsigned int nr_bytes,
2173 unsigned int bidi_bytes)
2175 if (blk_update_request(rq, error, nr_bytes))
2178 /* Bidi request must be completed as a whole */
2179 if (unlikely(blk_bidi_rq(rq)) &&
2180 blk_update_request(rq->next_rq, error, bidi_bytes))
2183 if (blk_queue_add_random(rq->q))
2184 add_disk_randomness(rq->rq_disk);
2190 * blk_unprep_request - unprepare a request
2193 * This function makes a request ready for complete resubmission (or
2194 * completion). It happens only after all error handling is complete,
2195 * so represents the appropriate moment to deallocate any resources
2196 * that were allocated to the request in the prep_rq_fn. The queue
2197 * lock is held when calling this.
2199 void blk_unprep_request(struct request *req)
2201 struct request_queue *q = req->q;
2203 req->cmd_flags &= ~REQ_DONTPREP;
2204 if (q->unprep_rq_fn)
2205 q->unprep_rq_fn(q, req);
2207 EXPORT_SYMBOL_GPL(blk_unprep_request);
2210 * queue lock must be held
2212 static void blk_finish_request(struct request *req, int error)
2214 if (blk_rq_tagged(req))
2215 blk_queue_end_tag(req->q, req);
2217 BUG_ON(blk_queued_rq(req));
2219 if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2220 laptop_io_completion(&req->q->backing_dev_info);
2222 blk_delete_timer(req);
2224 if (req->cmd_flags & REQ_DONTPREP)
2225 blk_unprep_request(req);
2228 blk_account_io_done(req);
2231 req->end_io(req, error);
2233 if (blk_bidi_rq(req))
2234 __blk_put_request(req->next_rq->q, req->next_rq);
2236 __blk_put_request(req->q, req);
2241 * blk_end_bidi_request - Complete a bidi request
2242 * @rq: the request to complete
2243 * @error: %0 for success, < %0 for error
2244 * @nr_bytes: number of bytes to complete @rq
2245 * @bidi_bytes: number of bytes to complete @rq->next_rq
2248 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2249 * Drivers that supports bidi can safely call this member for any
2250 * type of request, bidi or uni. In the later case @bidi_bytes is
2254 * %false - we are done with this request
2255 * %true - still buffers pending for this request
2257 static bool blk_end_bidi_request(struct request *rq, int error,
2258 unsigned int nr_bytes, unsigned int bidi_bytes)
2260 struct request_queue *q = rq->q;
2261 unsigned long flags;
2263 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2266 spin_lock_irqsave(q->queue_lock, flags);
2267 blk_finish_request(rq, error);
2268 spin_unlock_irqrestore(q->queue_lock, flags);
2274 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2275 * @rq: the request to complete
2276 * @error: %0 for success, < %0 for error
2277 * @nr_bytes: number of bytes to complete @rq
2278 * @bidi_bytes: number of bytes to complete @rq->next_rq
2281 * Identical to blk_end_bidi_request() except that queue lock is
2282 * assumed to be locked on entry and remains so on return.
2285 * %false - we are done with this request
2286 * %true - still buffers pending for this request
2288 static bool __blk_end_bidi_request(struct request *rq, int error,
2289 unsigned int nr_bytes, unsigned int bidi_bytes)
2291 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2294 blk_finish_request(rq, error);
2300 * blk_end_request - Helper function for drivers to complete the request.
2301 * @rq: the request being processed
2302 * @error: %0 for success, < %0 for error
2303 * @nr_bytes: number of bytes to complete
2306 * Ends I/O on a number of bytes attached to @rq.
2307 * If @rq has leftover, sets it up for the next range of segments.
2310 * %false - we are done with this request
2311 * %true - still buffers pending for this request
2313 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2315 return blk_end_bidi_request(rq, error, nr_bytes, 0);
2317 EXPORT_SYMBOL(blk_end_request);
2320 * blk_end_request_all - Helper function for drives to finish the request.
2321 * @rq: the request to finish
2322 * @error: %0 for success, < %0 for error
2325 * Completely finish @rq.
2327 void blk_end_request_all(struct request *rq, int error)
2330 unsigned int bidi_bytes = 0;
2332 if (unlikely(blk_bidi_rq(rq)))
2333 bidi_bytes = blk_rq_bytes(rq->next_rq);
2335 pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2338 EXPORT_SYMBOL(blk_end_request_all);
2341 * blk_end_request_cur - Helper function to finish the current request chunk.
2342 * @rq: the request to finish the current chunk for
2343 * @error: %0 for success, < %0 for error
2346 * Complete the current consecutively mapped chunk from @rq.
2349 * %false - we are done with this request
2350 * %true - still buffers pending for this request
2352 bool blk_end_request_cur(struct request *rq, int error)
2354 return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2356 EXPORT_SYMBOL(blk_end_request_cur);
2359 * blk_end_request_err - Finish a request till the next failure boundary.
2360 * @rq: the request to finish till the next failure boundary for
2361 * @error: must be negative errno
2364 * Complete @rq till the next failure boundary.
2367 * %false - we are done with this request
2368 * %true - still buffers pending for this request
2370 bool blk_end_request_err(struct request *rq, int error)
2372 WARN_ON(error >= 0);
2373 return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2375 EXPORT_SYMBOL_GPL(blk_end_request_err);
2378 * __blk_end_request - Helper function for drivers to complete the request.
2379 * @rq: the request being processed
2380 * @error: %0 for success, < %0 for error
2381 * @nr_bytes: number of bytes to complete
2384 * Must be called with queue lock held unlike blk_end_request().
2387 * %false - we are done with this request
2388 * %true - still buffers pending for this request
2390 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2392 return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2394 EXPORT_SYMBOL(__blk_end_request);
2397 * __blk_end_request_all - Helper function for drives to finish the request.
2398 * @rq: the request to finish
2399 * @error: %0 for success, < %0 for error
2402 * Completely finish @rq. Must be called with queue lock held.
2404 void __blk_end_request_all(struct request *rq, int error)
2407 unsigned int bidi_bytes = 0;
2409 if (unlikely(blk_bidi_rq(rq)))
2410 bidi_bytes = blk_rq_bytes(rq->next_rq);
2412 pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2415 EXPORT_SYMBOL(__blk_end_request_all);
2418 * __blk_end_request_cur - Helper function to finish the current request chunk.
2419 * @rq: the request to finish the current chunk for
2420 * @error: %0 for success, < %0 for error
2423 * Complete the current consecutively mapped chunk from @rq. Must
2424 * be called with queue lock held.
2427 * %false - we are done with this request
2428 * %true - still buffers pending for this request
2430 bool __blk_end_request_cur(struct request *rq, int error)
2432 return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2434 EXPORT_SYMBOL(__blk_end_request_cur);
2437 * __blk_end_request_err - Finish a request till the next failure boundary.
2438 * @rq: the request to finish till the next failure boundary for
2439 * @error: must be negative errno
2442 * Complete @rq till the next failure boundary. Must be called
2443 * with queue lock held.
2446 * %false - we are done with this request
2447 * %true - still buffers pending for this request
2449 bool __blk_end_request_err(struct request *rq, int error)
2451 WARN_ON(error >= 0);
2452 return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2454 EXPORT_SYMBOL_GPL(__blk_end_request_err);
2456 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2459 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2460 rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2462 if (bio_has_data(bio)) {
2463 rq->nr_phys_segments = bio_phys_segments(q, bio);
2464 rq->buffer = bio_data(bio);
2466 rq->__data_len = bio->bi_size;
2467 rq->bio = rq->biotail = bio;
2470 rq->rq_disk = bio->bi_bdev->bd_disk;
2473 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2475 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2476 * @rq: the request to be flushed
2479 * Flush all pages in @rq.
2481 void rq_flush_dcache_pages(struct request *rq)
2483 struct req_iterator iter;
2484 struct bio_vec *bvec;
2486 rq_for_each_segment(bvec, rq, iter)
2487 flush_dcache_page(bvec->bv_page);
2489 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2493 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2494 * @q : the queue of the device being checked
2497 * Check if underlying low-level drivers of a device are busy.
2498 * If the drivers want to export their busy state, they must set own
2499 * exporting function using blk_queue_lld_busy() first.
2501 * Basically, this function is used only by request stacking drivers
2502 * to stop dispatching requests to underlying devices when underlying
2503 * devices are busy. This behavior helps more I/O merging on the queue
2504 * of the request stacking driver and prevents I/O throughput regression
2505 * on burst I/O load.
2508 * 0 - Not busy (The request stacking driver should dispatch request)
2509 * 1 - Busy (The request stacking driver should stop dispatching request)
2511 int blk_lld_busy(struct request_queue *q)
2514 return q->lld_busy_fn(q);
2518 EXPORT_SYMBOL_GPL(blk_lld_busy);
2521 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2522 * @rq: the clone request to be cleaned up
2525 * Free all bios in @rq for a cloned request.
2527 void blk_rq_unprep_clone(struct request *rq)
2531 while ((bio = rq->bio) != NULL) {
2532 rq->bio = bio->bi_next;
2537 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2540 * Copy attributes of the original request to the clone request.
2541 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2543 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2545 dst->cpu = src->cpu;
2546 dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2547 dst->cmd_type = src->cmd_type;
2548 dst->__sector = blk_rq_pos(src);
2549 dst->__data_len = blk_rq_bytes(src);
2550 dst->nr_phys_segments = src->nr_phys_segments;
2551 dst->ioprio = src->ioprio;
2552 dst->extra_len = src->extra_len;
2556 * blk_rq_prep_clone - Helper function to setup clone request
2557 * @rq: the request to be setup
2558 * @rq_src: original request to be cloned
2559 * @bs: bio_set that bios for clone are allocated from
2560 * @gfp_mask: memory allocation mask for bio
2561 * @bio_ctr: setup function to be called for each clone bio.
2562 * Returns %0 for success, non %0 for failure.
2563 * @data: private data to be passed to @bio_ctr
2566 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2567 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2568 * are not copied, and copying such parts is the caller's responsibility.
2569 * Also, pages which the original bios are pointing to are not copied
2570 * and the cloned bios just point same pages.
2571 * So cloned bios must be completed before original bios, which means
2572 * the caller must complete @rq before @rq_src.
2574 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2575 struct bio_set *bs, gfp_t gfp_mask,
2576 int (*bio_ctr)(struct bio *, struct bio *, void *),
2579 struct bio *bio, *bio_src;
2584 blk_rq_init(NULL, rq);
2586 __rq_for_each_bio(bio_src, rq_src) {
2587 bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2591 __bio_clone(bio, bio_src);
2593 if (bio_integrity(bio_src) &&
2594 bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2597 if (bio_ctr && bio_ctr(bio, bio_src, data))
2601 rq->biotail->bi_next = bio;
2604 rq->bio = rq->biotail = bio;
2607 __blk_rq_prep_clone(rq, rq_src);
2614 blk_rq_unprep_clone(rq);
2618 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2620 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2622 return queue_work(kblockd_workqueue, work);
2624 EXPORT_SYMBOL(kblockd_schedule_work);
2626 int kblockd_schedule_delayed_work(struct request_queue *q,
2627 struct delayed_work *dwork, unsigned long delay)
2629 return queue_delayed_work(kblockd_workqueue, dwork, delay);
2631 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2633 #define PLUG_MAGIC 0x91827364
2635 void blk_start_plug(struct blk_plug *plug)
2637 struct task_struct *tsk = current;
2639 plug->magic = PLUG_MAGIC;
2640 INIT_LIST_HEAD(&plug->list);
2641 INIT_LIST_HEAD(&plug->cb_list);
2642 plug->should_sort = 0;
2645 * If this is a nested plug, don't actually assign it. It will be
2646 * flushed on its own.
2650 * Store ordering should not be needed here, since a potential
2651 * preempt will imply a full memory barrier
2656 EXPORT_SYMBOL(blk_start_plug);
2658 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2660 struct request *rqa = container_of(a, struct request, queuelist);
2661 struct request *rqb = container_of(b, struct request, queuelist);
2663 return !(rqa->q <= rqb->q);
2667 * If 'from_schedule' is true, then postpone the dispatch of requests
2668 * until a safe kblockd context. We due this to avoid accidental big
2669 * additional stack usage in driver dispatch, in places where the originally
2670 * plugger did not intend it.
2672 static void queue_unplugged(struct request_queue *q, unsigned int depth,
2674 __releases(q->queue_lock)
2676 trace_block_unplug(q, depth, !from_schedule);
2679 * If we are punting this to kblockd, then we can safely drop
2680 * the queue_lock before waking kblockd (which needs to take
2683 if (from_schedule) {
2684 spin_unlock(q->queue_lock);
2685 blk_run_queue_async(q);
2688 spin_unlock(q->queue_lock);
2693 static void flush_plug_callbacks(struct blk_plug *plug)
2695 LIST_HEAD(callbacks);
2697 if (list_empty(&plug->cb_list))
2700 list_splice_init(&plug->cb_list, &callbacks);
2702 while (!list_empty(&callbacks)) {
2703 struct blk_plug_cb *cb = list_first_entry(&callbacks,
2706 list_del(&cb->list);
2711 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2713 struct request_queue *q;
2714 unsigned long flags;
2719 BUG_ON(plug->magic != PLUG_MAGIC);
2721 flush_plug_callbacks(plug);
2722 if (list_empty(&plug->list))
2725 list_splice_init(&plug->list, &list);
2727 if (plug->should_sort) {
2728 list_sort(NULL, &list, plug_rq_cmp);
2729 plug->should_sort = 0;
2736 * Save and disable interrupts here, to avoid doing it for every
2737 * queue lock we have to take.
2739 local_irq_save(flags);
2740 while (!list_empty(&list)) {
2741 rq = list_entry_rq(list.next);
2742 list_del_init(&rq->queuelist);
2746 * This drops the queue lock
2749 queue_unplugged(q, depth, from_schedule);
2752 spin_lock(q->queue_lock);
2755 * rq is already accounted, so use raw insert
2757 if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
2758 __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
2760 __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
2766 * This drops the queue lock
2769 queue_unplugged(q, depth, from_schedule);
2771 local_irq_restore(flags);
2774 void blk_finish_plug(struct blk_plug *plug)
2776 blk_flush_plug_list(plug, false);
2778 if (plug == current->plug)
2779 current->plug = NULL;
2781 EXPORT_SYMBOL(blk_finish_plug);
2783 int __init blk_dev_init(void)
2785 BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2786 sizeof(((struct request *)0)->cmd_flags));
2788 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
2789 kblockd_workqueue = alloc_workqueue("kblockd",
2790 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
2791 if (!kblockd_workqueue)
2792 panic("Failed to create kblockd\n");
2794 request_cachep = kmem_cache_create("blkdev_requests",
2795 sizeof(struct request), 0, SLAB_PANIC, NULL);
2797 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2798 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);